Gemstone Tutor Reborn
by BrownieFox
Summary: Tsuna is half gem. Or well, like, 5% gem. But he was a gem and that's what counts. Too bad he knows nothing about it and is getting involved into the mafia while he's at it.
1. Chapter 1

**A/N: Hey, Browniefox here! Yep, still alive and kicking.**

 **So, what have I been working on instead of re-reading the manga and working on Parallel Worlds?**

 **Playing with the part I sort of know and creating this au!**

 **There'll be a sort of explanation at the end in another author note, and if anybody wants to know more just message me, I'm happy to tell! I just don't want to spoil it for those that care.**

 **Please enjoy!**

* * *

" _Papa!" Tsuna ran towards Iemitsu, who had just walked through the front door._

" _Tuna Fish!" Iemitsu picked his son up, holding him over his head and grinning up at him. "Did you miss Papa?"_

" _Uh-huh!" Tsuna nodded vigorously._

" _How much?"_

" _This much!" He spread his arms wide, giggling._

" _I'm so glad to see how loving your son is." An old man walked up behind Iemitsu._

" _Papa, who's that?" Tsuna asked, shying away slightly from the stranger._

" _This is Timoteo, he's like your grandpa." Iemitsu set his son on the ground. Timoteo stepped forward, kneeling down so he was at Tsuna's level. Tsuna quickly hid behind his father's legs._

" _It's okay," The old man coaxed, putting a hand out, "I can even prove it."_

 _Tsuna looked up at Iemitsu, who nodded encouragingly. Cautiously, he put his small hand into Timoteo's. Timoteo gently grasped it, as gently as his severely calloused hands could, and slowly, slowly brought Tsuna forward until the child's hand touched just over the man's hip. Instead of touching something squishy, however, it was something hard and solid. Fear at least momentarily forgotten, Tsuna's hand curiously explored the area, feeling angles._

" _Papa, papa, he has one too!" Tsuna cheered before slapping his hands over his mouth. Iemitsu laughed._

" _It's okay, Timoteo is okay to talk about it around. In fact, Timoteo wants to see your gem. Can you show him your gem?" Tsuna nodded, and after a moment's hesitation pulled down the front of his hoodie, revealing an orange gem._

" _He has a lot of potential. Are you sure about this Iemitsu?" Iemitsu nodded. By this time they had gone to the backyard, Tsuna sitting in Timoteo's lap, having completely gotten over his original wariness of the man._

" _Yes. You said it yourself, he has a kind heart. He's a very loving boy. The mafia would tear him apart without a second thought. It's best if he stays out of it, and his gemstone,_ my _gemstone, will drag him in. It's best if you do all you can to keep him safe. I would do it myself, but..." Iemitsu rubbed his chest. Timoteo sighed. Could Iemitsu really not see the gap this would create this his family? Or was it a sacrifice he was willing to make. Nevertheless, Timoteo had known when he came what Iemitsu wanted him to do, and he had asked Lal Mirch what she knew about it before coming._

 _Timoteo carefully crafted a bubble in his hands and placed it over Tsuna's gem. It covered the surface seamlessly. Tsuna's eyes fluttered slightly before closing altogether. It was done._

" _Supposedly, his gem should be suppressed. He'll live, obviously, but this has never been done before. We don't know what the repercussions will be." Timoteo cradled the child in his arms. He didn't agree with this in the slightest, but Tsuna wasn't his child and this wasn't his choice._

 _oOo_

If Tsuna knew what was going to happen after he opened the door, he wouldn't've and instead barricaded the door.

Or perhaps, if he knew enough about what happened, he would've thrown the door open and greeted the change with open arms.

As it goes, when the doorbell rings, Tsuna opened the door a bit slowly. While bullies had never come to his home before, Tsuna wouldn't put it past them. But there were no bullies. Instead, he found a baby. For a baby, he was very smartly dressed in a suit and a fedora. Sitting on the brim of said fedora was a lizard-gecko-thing that almost looked like it had a lazy smile on its face. Tsuna's eyes were drawn most to the yellow stone encompassed in a silvery done that rested on the baby's left hip.

"Ciaossu," The baby smiled, "I am Reborn, your home tutor."

"Uh," Tsuna stared at 'Reborn' for a moment before turning his head back inside. "MOM!"

"Yes, Tsuna?"

"A little kid's lost." Tsuna pointed at Reborn. He wasn't prepared for when Reborn jumped and kicked his side, sending the teen well into the house, landing against the stairs. His mother, the sweet, naive woman she was, didn't take note of that. She was more concerned about fawning over how cute and adorable Reborn was.

"Oh, didn't I tell you? I got you a tutor. All he needs is meal and rooming. He'd perfect! And so young and cute too!"

"I might say the same about you, Mrs. Sawada." Reborn replied and Nana blushed.

"And so smooth. Please, call me nana. You'll be sleeping Tsuna's room. Why don't you go ahead and make yourself at home until dinner's ready?"

"Thank you, Nana." Reborn bowed and then went part way up the stairs before pausing. "Tsuna, why don't you come up here too?"

A sense of foreboding crawled up Tsuna's spine, and for a moment he contemplated booking it in the opposite direction. The throbbing in his side hinted that that might not be a great idea. Tsuna followed the baby up the stairs like he was going to his own funeral. Upstairs, the baby climbed onto Tsuna's bed, watching the teenager expectantly. Tsuna shifted nervously. Despite his abysmal grades, he'd never had a tutor before and wasn't really sure how this was supposed to work. Not to mention the tutor was a baby, which was very questionable.

"S-so, what are you tutoring m-me on?" The silence had gotten awkward ages ago.

"To be a mafia boss."

Cherry on top of the weird sundae.

"M-m-mafia?!" Tsuna shrieked. He was quickly shut up as two bullets lodged into the wall on either side of his head. There was a gun in Reborn's hand, and as Tsuna watched, it glowed and changed into the reptile that had been on Reborn's hat.

"Yes, mafia. You are to be the next don of the most powerful mafia famiglia, the Vongola." Reborn declared.

"B-but I'm dame-Tsuna! Isn't there anyone e-else?" Tsuna asked desperately. Sure his life sucked, but surely being involved in mafia would make it suck even more.

"The current Head did have four sons. Enrico was killed in a gunfight, Massimo was drowned, all that was found of Fredrico was his bones, and the fourth is eligible and currently out of commision. Your father would come after them, but his position, which he refuses to give up, makes him unable to take the mantle. As his son, you are the next and only candidate for Vongola Decimo." Tsuna could only stare in shock at the baby.

Then Nana called up that dinner was ready.

oOo

Tsuna was awoken the next morning by a hammer bashed into his skull.

Reborn declared that Tsuna would no longer be waking up late. No respectable boss was late. He then proceeded firing bullets at Tsuna ll through his morning routine. His mom didn't seem overly worried about it, though, and just wished him a good day as he left. The morning had been hectic, but it was almost worth it to be able to walk to school instead of sprint.

Then he saw her.

Walking on the other side of the road and ahead of him was the class idol, Kyoko Sasagawa.

"You like her."

"H-huh?!" Reborn, who had been walking the fence adjacent to Tsuna, hopped down in front of him and looked up at the decimo expectantly.

"Go confess to her." Reborn's face required passive, but there was an unsettling glint to them.

"W-what?! No way!" Tsuna's eyes widened in terror at the sheer thought of doing so. The baby jumped up and grabbed Tsuna's hand, flinging the student across the road. Tsuna let out a high-pitched scream. Kyoko turned around at the sound, just in time to see Tsuna as he impacted into her, sending them both sprawling onto the ground. Tsuna quickly climbed to his feet and started to stammer out an apology when his chest fluttered. A sudden burst of confidence resonated from there, and before he knew it, the words came spilling out.

"K-kyoko, will you g-go on a date with me?" The teens stared at each other for a moment, neither quite realizing what had just happened. It seemed to sink into tsuna first, as his face became bright crimson and he let out at earsplitting screech, running as far away from Kyoko as he could. He collapsed a good distance from her, panting and pinching himself. This had to be a dream. A weird nightmare/dream thing. He knew better than to confess to Kyoko.

"How rude." Tsuna stiffened before slowly turning his head. Reborn. The infant stood there, smiling innocently. "I never took you as the kind to ask a girl out and then abandon her before she could even give you an answer."

"W-wha-, th-that, I-I-" Tsuna spluttered. Reborn's smile twitched into a smirk. Something clicked in his head. "It was you! You, you did s-someth-thing…" Tsuna quickly lost conviction in that idea. That was stupid. Reborn just threw him. But Reborn nodded.

"I synced with your gem." Tsuna's hand went to his chest, the rock that nobody had explained or could explain. His mother had simply said he had it genetically from his dad, who up until last night, he had thought to be dead. Though apparently he was alive and working.

"W-what do you mean?"

"I matched up to you like when two gems fuse. But instead of fusing, I used it to help trigger your abilities and other such repressed things."

"Fuse? Wh-what, how?" Reborn raised an eyebrow.

"If you don't hurry, you'll be late for school."

So much for not running to school.

* * *

 **A/N: So, the most basic of the explanation: Tsuna's gem and all his guardians have gems that belonged to the first Vongola Famiglia (I know, a shocker and twist!). The Ninth did a sort of half-bubble of Tsuna's gem, repressing his gem related powers and abilities (as explained in the chapter). This sort of parallels the whole sealing of the flames, obviously. Timoteo studied Lal for it oooooooh wonder what that means~**

 **Brief summary of chapter:**

 **G E M S**

 **Gun-gecko is best gecko**

 **Yay confusion**

 **totally making things up as I go**


	2. Chapter 2

In a dead sprint, Tsuna was able to make it into the building just as the bell rung. He'd still be late, but usually Hibari wasn't patrolling the inside at this time, so Tsuna would be saved a beating. He was mocked by all as he entered the classroom, but it was the normal amount of mocking. His confession to Kyoko hadn't gotten around yet, and maybe if he was lucky it never would. He'd be able to brush off the morning like it had never happened.

Of course, that would require Tsuna being lucky. And Tsuna was never lucky.

During lunch, Mochida stalked up to Tsuna, tall and intimidating. Kyoko could be seen behind him, begging him to let it go.

"I heard you hit on my girl." Mochida growled, which was followed by a 'She's not your possesion!' from Hana.

"N-n, I-I w-would n-n-n-" Tsuna struggled to word but it was hard when he was panicing.

"Don't try denying it, _dame_ -Tsuna." Mochida sneered, shoving the weak boy. "Did you actually think you stood a chance with her? A no-good dame like you?" Tsuna's eyes were firmly on the ground, his entire body shaking in fear. "If you really want her, you'll have to fight me for her. One hour after school, meet me in the gym. Kendo. Kyoko's the prize."

Mochida continually leaned closer to Tsuna as Tsuna steadily leaded farther and farther back.

"I can't believe I have to deal with you monkeys! You're all so immature!" Hana huffed, pulling Kyoko away from the conversation. Luckily, lunch ended shortly after that and Tsuna got a break from being leered at from directly below Mochida to being glared at by the rest of his classmates for the school day.

Running was an option, Mochida would find him, After this wasn't just about Kyoko. This was about dame-Tsuna thinking he'd had a chance with her. This was about Tsuna attempting to climb just a little higher on the social ladder when everyone knew he was the lowest, the punching bag, the most useless of the students. This match was to make sure Tsuna remembered his place without ruining Mochida's own social standing or risking getting caught bullying by a teacher that cared.

The gym was crowded when Tsuna got there, and with each step he shrunk further and further into himself. They handed him the 'protective gear', though it felt suspiciously heavy. Tsuna let out a breath, preparing himself for the coming bruises. That's when something caught his eye. Above the gym, in the rafters, was Reborn. The gem on his hip was glowing, as was the silver bubble around it. And with it came the tingling in his chest.

Without thinking, Tsuna surged forward.

Mochida was surprised, but lifted his bokken to block. He wasn't captain of the Kendo club for nothing. Unfortunately, he wasn't prepared to handle the energy surging through Tsuna. Every muscle was stimulated. He ran forward and landed a solid hit on the older boy. When that didn't get him a point, he knocked Mochida onto his stomach. This continued until he was pulling on the Kendo Captain's hair and finally got the point, winning the match.

It was like a door had been slammed shut. A switch turned off. The strength left him, the tingling disappeared. He hadn't realized how bright the world had seemed in that one moment compared to the rest of his life.

"Oh my gosh, you were amazing!" Kyoko ran forward. "I never knew you were that strong. Well, I better make sure Mochida-senpai is alright." Tsuna, still stunned by the fact that Kyoko had just talked to him, jumped as Hana came into view, glaring.

"Hey, just because you won doesn't mean Kyoko is 'yours' or whatever, got it?" Tsuna nodded vigorously. Slowly, the crowd dispersed, leaving Tsuna standing alone in the gym. His hand drifted to his gem.

"Come on, you still have homework and studying."

Reborn stood at the gym entrance, gun in hand.

oOo

When Gokudera arrived, Tsuna felt a dull humming from his gem.

The boy was intimidating. He looked like a delinquent, a permanent scowl on his face, baggy clothes, bad personality, and the one time he brought his hands out of his pockets, the guy was wearing fingerless gloves. He showed a particular interest in Tsuna by knocking his desk over, but seemed uninterested in just about everybody else. After school, Tsuna honestly tried to just run home and get away from the Gokudera kid. However, the guy cornered him by one of the walls. His scowl was like daggers, and the humming in Tsuna's chest got worse.

"So this is him? Sawada Tsunayoshi, the Vongola Decimo."

Reborn hopped onto the delinquent's shoulder

"Yep."

"If I beat him, you'll really give me his position?"

"Already talked it over with the ninth." Tsuna, for his part, was shocked and scared. He thought he was the only one who could be the next boss. Though he would gladly hand over the position to Gokudera if that really was an option.

"This shouldn't take too long." And from seemingly nowhere, Gokudera pulled out sticks of dynamite. The cigarette dangling from his mouth lit their fuses and he tossed them to Tsuna. Tsuna darted out of the way, only for Gokudera to pull out even more dynamites.

"He's called Smokin' Bomb Hayato." Reborn was now standing off to the side of the fight, watching it with seemingly no worry. "He's able to hide enough explosives on his person to explode entire towns if he so desired." Which definitely seemed right. Barrage after barrage of tnt was thrown, exploding in the schoolyard. Tsuna ran around, terrified of being burned and exploded.

Tsuna's chest sparked.

He needed to defuse the dynamites.

With abnormal speed, he lept forward, putting out any fuse his fingers landed on. He barely was aware of what he was doing, yet at the same time his senses were heightened. Through a muffled clarity, Tsuna heard Gokudera call out his triple bomb attack. He watched as one, then two, then the entire armful of explosives fell to Gokudera's feet. He knew without a doubt that he could easily get a safe distance from the dynamite, but the thought barely crossed his mind.

When everything snapped back into reality, Tsuna was sitting on the ground. Gokudera was also on the ground, in front of him, the constant glare gone from his face, eyes wide and staring at Tsuna. The two teenagers were surrounded by faintly-smoking dynamite sticks.

"Ah, s-sorry." Tsuna wasn't sure what he was apologizing for, but he messed up all the time so there was probably something.

"You saved me." Gokudera's voice was filled with awe. The glare still hadn't returned.

"Yes?" Not that it was really Tsuna, it was his special rock powers mixed with Reborn's… whatever he did.

"Truly, you will be a great boss. It would be an honor to serve in your famiglia. I promise to be nothing less than your right-hand man, dedicated to you." Needless to say, Tsuna was shocked by the hitman's sudden change in attitude. The boy was now bowing, head smacking into the ground.

"B-but I thought _you_ wanted to be the tenth boss! You can have the position! I don't want it!" Tsuna's confusion was only growing.

"I didn't actually want the position. When I heard the heir to the Vongola was around my age, I wanted to see how strong he was compared to myself. And now I know he's someone worth following. Someone worthy of my respect." The hitman's eyes were sparkling, but something was bothering Tsuna still. Something telling him that there was more to the story.

Gokudera's left hand nervously scratched at the palm of his right.

oOo

Gokudera basically became Tsuna's body guard, which Gokudera, seemed to think he really was. Every morning, Tsuna was awoken by Reborn in various painful ways, ate breakfast, and was greeted by his self-proclaimed new best friend on his way to school. Bullying on Tsuna went down to nearly nothing when Gokudera was around, as he beat up anyone that went after Tsuna. After school, Gokudera followed Tsuna home like a loyal dog and chilled there for the majority of the afternoon. Unfortunately, Tsuna's new friend refused to fight Reborn. He supported Reborn's claim of being the number one hitman and actually joined in somewhat on the lessons. The teaching part. Because delinquent-Hayato also turned out to be a genius.

Some time after dinner, Gokudera would go back to wherever it was he lived and leave Tsuna to 'study' more.

Progress in legitimate subjects that were covered in school was going by at a snail's pace. But, against all of Tsuna's better judgement, he did find some of the mafia subjects to be intriguing, even as his brain rejected the idea of being involved in such terrible things. One of these subjects was the current generation of Vongola. The ninth boss was named Timoteo and honestly looked like a good-natured grandfather. He had white hair, a mustache, and eyes that sparkled with an untold joke and were surrounded by laugh lines. Reborn warned him not to be fooled, the old man was an extremely formidable opponent, a master of manipulation, and should not be taken lightly.

Eventually, Tsuna asked Reborn what he knew about his gem.

Reborn declared it a subject for another day, but did explain a few things. The gem was hereditary, and this far down the line the parent could choose whether or not to give it to their child, though their health may be affected by doing so. Supposedly two people with gems could combine their strength together, or as Reborn had put it, fuse. While Reborn had the ability to resonate with Tsuna, he did 'fuse' with him, but brought the dormant power of the gem out of Tsuna and able to be used. By the end of his teaching, Tsuna would be able to do it himself and much more.

Tsuna asked about Reborn's gem.

Reborn brought out his gun and said that that was enough for today.

oOo

 _One-hundred-thirty years ago_

 _(omake)_

OoO

The first to corrupt had been Rhodolite.

He'd always had a fair amount of foresight, and many of the others wondered if he had seen this coming.

When he had felt the corruption start pressing at him, into gem, he'd distanced himself from the others.

"I always fancied us Icarus. Now, we must burn."

He did not fuse with any of them again, instead adopting his meditation pose. He would corrupt, but he was going to do what it took to make it take as long as possible. This was his only solace, a final victory.

Even corrupted, the others stayed by him.

The next had been Amber.

Her corruption had been far less of a surprise. More experimental than all the others, she had been a replacement. As the corruption started to take over her form, she'd fled from the others until she found him. The one who had created their kindergartens. The one who hadn't warned them of this but knew it was nigh inevitable.

He'd picked her up, and he felt legitimate sorrow for her.

She'd comforted him.

"I know you wanted to protect her, but we both knew I could never be enough."

He shed a tear as she corrupted.

Yellow Bowenite took the corruption in stride.

Unlike the others, he literally hadn't been made for battle, though that didn't stop him. His purpose was to create things, and create he did. But he was also gifted in shape shifting, changing his form on a whim.

"I take pride in my shifting. This is simply another form."

He'd given the others a lazy, reassuring smile.

The corruption hit him harder than Rhodolite.

His screams spoke of the how terrible the corruption could be.

Emerald had been prepared.

He wanted to go out with a bang, and attacked a village as he corrupted.

The one who had made them was forced to intervene, seeing as, while his friends didn't necessarily think that it was the right choice of action, the ones that really worked as the conscience of the group had been corrupted already.

As Emerald was injured enough to put his physical form out of commision, he took the time to look that man in the eyes.

"You always complain I bite the hand that made me. At least as a corruption I don't have to even pretend to _heed_ it."

The man left after bubbling Emerald's gem.

When Blue Hawk's Eye began to corrupt, he did as Amber did.

He went off to find the man.

But his plan wasn't say goodbye. The gem was looking for a fight, a different kind of goodbye that was more of a final 'F*** You' than anything else.

He took the corrupted Yellow Bowenite with him. Even as a corruption, Yellow Bowenite was a very placid gem, but he also seemed to retain some semblance of who he used to be, as when Blue Hawk's Eye called for him to battle, he responded readily.

Of course, it didn't take long for them to be taken down, but seeing as Blue Hawk's Eye was corrupting any way, he took it as a final chance to fuse with one whose company he had enjoyed greatly.

"As a sane gem or a tortured corruption, don't doubt my ability to hunt you down and make you pay for our creation."

He had spat as his form shifted and his mind warped.

When Iolite corrupted, they did it quietly.

They carefully acted like they didn't care, sitting still as their form shifted.

Corrupted Rhodolite was nearby, watching them carefully, and even as a corruption those eyes seemed to hold so much wisdom and knowledge. The one who had yet to corrupt went over to them, sitting next to them, hand placed carefully right next to theirs.

They looked at him.

He hated talking, but his eyes conveyed enough.

"Of course I'm not afraid. Though, if it would make you feel better… hold me?"

He held them in his arms as they corrupted,

Mojave Turquoise was alone.

Sure, Iolite and Rhodolite's corrupted forms were there, but they were corrupted. With every passing day they seemed to become more wild and animalistic.

He cried when he felt the corruption tearing away at himself.

The corrupted forms sensed his distress and went over to him, encircling him what were supposed to comforting. And it was. But it was also a constant reminder that this was the end. What he was going to become.

They looked at him curiously, silently asked what was wrong as they no longer had the ability to talk.

He ripped off the cloth that covered his mouth. He had formed it there himself, but now it seemed like it was threatening to choke his entire being just as much as the corruption was.

"I-I'm not ready! I-if I corrupt, if I leave, who will remember us?"

His sobs only ceased when his form changed to one that lacked vocal chords.

oOo

 **A/N: 4561234578926555 not real bucks to whoever can guess who the people in the omake-thing is. Technically not an omake, I think, since these are legit characters and events in the au, but it also doesn't really go along with what's happening right how in the story. I just liked these characters too much to not show them off a bit.**

 **ANY WAY, tell me if you like story, if you have any opinions on lore or how powers work of it you're confused please say something, I'd love to hear.**


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